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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
  1. GRB 251205A: COLIBRÍ optical observations
  2. GRB 251205A: GOTO optical afterglow detection
  3. GRB 251205A: NOT optical observations
  4. GRB 251205A: GTC/OSIRIS+ redshift z = 1.100
  5. GRB 251205A: Enhanced Swift-XRT position
  6. Swift GRB 251205A : MASTER OT detection with host galaxy
  7. GRB 251205A: Swift detection of a burst with an optical afterglow
  8. Swift GRB251205A: Global MASTER-Net observations report
  9. GRB 251126B: Fermi GBM Final Localization
  10. GRB 251203A: Insight-HXMT/HE detection
  11. GRB 251203C: SVOM/ECLAIRs refined analysis
  12. SVOM/sb25120502: SVOM detection of a faint X-ray transient candidate
  13. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  14. GRB 251203C: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  15. GRB 251202A: SVOM/GRM observation
  16. GRB 251203A: GECAM-B observation of a burst
  17. GRB 251203A: SVOM/GRM observation
  18. GRB 251201B: SALT spectroscopic redshift z = 1.599
  19. GRB 251203C: J-band observations with WINTER
  20. GRB 251129B: Glowbug gamma-ray detection of a short burst
  21. GRB 251203A: AstroSat CZTI detection
  22. EP251130a: JinShan near-infrared observations
  23. Fermi Gamma-ray Burst Monitor trigger 786496343/251203967 is not a GRB
  24. GRB 251203C: LCO optical afterglow confirmation
  25. GRB 251203C: SVOM/VT optical counterpart
  26. GRB 251203C: EP-FXT follow-up observation
  27. GRB 251129A/EP251129a : SVOM/ECLAIRs refined analysis
  28. GRB 251129B: GECAM-B observation of a burst
  29. GRB 251203B: Swift-XRT observations
  30. GRB 251203B: confirmation of a stellar flare by BOOTES-2
  31. GRB 251203B : SVOM trigger sb25120304 is not a GRB
  32. GRB 251203C: LCO optical upper limits
  33. GRB 251203B: LCO optical upper limits
  34. GRB 251203B: SVOM/VT optical observation
  35. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  36. GRB 251203C: SVOM detection of a burst
  37. SVOM GRB251203.77: Global MASTER-Net observations report
  38. SVOM GRB251203B: Global MASTER-Net observations report
  39. GRB 251203B: SVOM detection of a burst
  40. GRB 251129A / EP251129a: SVOM/VT optical color bluer
  41. GRB 251201B: Insight-HXMT/HE detection
  42. EP251202a / GRB 251202A: Insight-HXMT/HE detection
  43. EP251130a: MAO/AZT-22 optical observations
  44. GRB 251203A: Fermi GBM Final Real-time Localization
  45. EP251202a / GRB251202A: AstroSat CZTI detection
  46. GRB 251202A / EP251202a: SVOM/VT optical observation
  47. GRB 251201B: Fermi GBM Observation
  48. EP251202a/GRB 251202A: KAIT optical observations
  49. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  50. Fermi GRB 251202B: Global MASTER-Net observations report
  51. GRB 251202B: Fermi GBM Final Real-time Localization
  52. IPN triangulation of GRB 251129B (short/hard)
  53. GRB251129A/EP251129a: Swift UVOT detection
  54. GRB 251129B: AstroSat CZTI detection
  55. GRB 251202A: Fermi GBM Observation
  56. GRB 251202A: Swift/UVOT Detection
  57. GRB 251201B: Kilonova-Catcher optical afterglow detection
  58. GRB 251201B: Swift/UVOT Detection
  59. GRB 251130B: Glowbug gamma-ray detection
  60. GRB 251201B: GECAM-B observation of a long burst
  61. EP251130a: continued NOT optical observations indicate steep fading phase
  62. GRB 251122A/EP251122a: CrAO ZTSh optical observations
  63. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  64. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  65. GRB 251202A: GOTO optical afterglow detection
  66. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  67. GRB 251201A: GECAM-B observation of a burst
  68. GRB 251126A: SAO RAS optical marginal detection
  69. GRB 251202A: Swift-XRT afterglow detection
  70. EP251129a/GRB 251129A: NOWT Detection
  71. GRB 251126A: SVOM/VT optical observation
  72. EP251130a: SVOM/VT optical observation
  73. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  74. Fermi GRB 251202A: Global MASTER-Net observations report
  75. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  76. GRB 251201B: Swift-XRT refined Analysis
  77. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  78. EP251202a/trigger 01709249064: Las Cumbres discovery of the optical counterpart
  79. GRB 251202A: Fermi GBM Final Real-time Localization
  80. GRB 251201A: SVOM/GRM observation of a burst
  81. GRB 251201B: SVOM/VT optical fading
  82. Swift GRB 251201B : MASTER optical counterpart detection
  83. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  84. Swift GRB 251201B: Global MASTER-Net observations report
  85. GRB 251201B: Enhanced Swift-XRT position
  86. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  87. GRB 251130B: AstroSat CZTI detection
  88. GRB 251201B: Swift detection of a burst with an optical counterpart
  89. GRB 251201B: Fermi GBM Final Real-time Localization
  90. EP251130a: Mondy optical observations
  91. EP251130a: Optical detections with Kinder observations
  92. SVOM GRB251201.19: Global MASTER-Net observations report
  93. EP251130a: SAO RAS optical observations
  94. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  95. EP251130a: KAIT optical observations
  96. EP251130A: Optical observation from 1.3m DFOT
  97. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  98. EP251130a: JinShan optical observations
  99. GRB 251201A: MAXI/GSC detection
  100. Fermi GRB 251130B: Global MASTER-Net observations report

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